This invention relates generally to a weather radar system having the capability of analyzing weather conditions. More particularly, this invention relates to a weather radar system configured for positioning the radar system antenna beam for the purposes described. Still more particularly, this invention relates to a weather radar system of the type described which features an automatic mode for enhancing weather condition analysis and reducing user workload.
Weather radar systems have different requirements depending upon the mission and/or end use of the system. For example, weather radar systems for marine or small aircraft applications are typically directed to detection and avoidance of threatening weather conditions. Systems for land based and medium to large aircraft applications are directed to both detection and analysis of weather conditions. In this regard, it is noted that the purpose of weather condition analysis is to provide weather warnings, as in land based radar applications, and to facilitate decisions to fly through or around weather disturbances, as in airborne radar applications.
To assess the threat of a weather condition, both reflectivity information, which relates to the rate of precipitation due to the weather condition, and information as to the height of the weather condition need to be taken into account. The user of conventional radar systems requires substantial training and experience to be able to accurately analyze a potential weather threat from this information. In the case of airborne radar, user workload is an important consideration as will be appreciated. This consideration is magnified when approaching and landing an aircraft under adverse weather conditions.
In regard to conventional weather radar systems, a user is provided with a single elevation (vertical) plan view on a display. That is to say, a view looking down, with the radar antenna scanning through an azimuth angle (horizontally) at a particular elevation angle. The elevation angle is manually controlled by the user and which control is usually referred to as "tilt control." The user must continually adjust the elevational or tilt of the display to obtain an impression of the height of the various weather conditions and their physical relationship to the user's position. The disadvantages of weather radar systems of the type described are as follows: (1) the single elevation plan view is the only information available at any give time; (2) user skill is required to effectively adjust the tilt of the display to perceive weather condition height information; and (3) continual tilt adjustment disadvantageously adds to the user's workload.
An improvement in the weather radar system art to avoid the aforenoted disadvantages features using the radar antenna in a vertical scanning (elevation)mode. This mode provides a vertical side view on the display at a given radial angle. Height versus range information is thus readily available to the user. The disadvantage to this approach is that the data is only applicable to a selected azimuth angle. Thus, the user is again required to exercise skill and constant attention to assess a weather condition at all azimuth angles.
A further improvement in the weather radar art is advanced in U.S. Pat. No. 4,940,987 (U.S. Class 342/26) issued to Frederick on Jul. 10, 1990. This approach features displaying two simultaneous views of a weather condition, i.e. a conventional plan view and a vertical side or frontal view. The net effect of this approach is to view a weather condition in two intersecting planes. One plane is a horizontal plan view, while the other plane is user selected as a vertical slice along the radar range axis, or a vertical slice perpendicular to said range axis. The vertical slices or views can be adjusted as to their thickness such that, for example, the frontal view represents an integration of the information from one range to another. The disadvantages of this approach are as follows: (1) the user update rate is slow because the antenna beam must be positioned to cover a full volume of space; (2) user interpretation is difficult because the data is included in two intersecting planes as aforenoted; (3) the user workload is high because of the required range or radial angle selection for the vertical slices or views; and (4) the radar system requires substantial hardware (memory) to support this approach.
Still another approach to the noted problem is advanced in U.S. Pat. No. 5,198,819 (U.S. Class 342/26) issued to Susnjara on Mar. 30, 1993. This approach stores multiple plan views in their own display memories. The views are then shown in overlapping fashion on the display, with only the highest of the stored views shown in true weather condition precipitation intensities. The concept of storage of multiple plan views suffers from a long lag time to fill all memory planes. Each horizontal scan usually takes several seconds to complete. Even if the currently scanned view is continuously updated, the displayed complete view has data that could be almost a minute old. This problem is especially evident when aircraft heading changes are made. Further, the overlapping views can lead to dangerous flight conditions for airborne weather systems, in that low altitude features can be overlooked. Also this concept is costly in that a memory plane is needed for all plan views. Finally, a display unit as required is complex and not readily available in current weather radar systems.
Accordingly, it is an object of this invention to provide an automatic mode of operation for positioning a radar antenna beam in the elevation axis while scanning the horizontal axis to avoid the disadvantages of the prior art.
It is another object of this invention to permit a user to select elevation axis scan limits and elevation axis scan increments to achieve the purposes of the invention.
It is still another object of this invention to provide an automatic mode of operation for the radar system which is user selectable such that activation is on demand as required, with conventional scanning being readily available.
It is yet another object of this invention to provide a weather radar system display that is easy to understand so as to minimize interpretation time.
It is a further object of this invention to minimize radar system hardware and to provide an approach which can be readily adapted to a conventional weather radar system.